A thought passed by me and I wondered if projecting black light was possible.
We can make lights with many other colors, but I'm not so sure about black.
So, is it possible? Has it been done?
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No, because black is not an "actual" color, but the absence of light. In other words, when you perceive a color it is because there is some electomagentic radiation that is bounced back from the object. Our retinas get exited and interptet that as a color (they interpret different colors in dependence of what frequencies are reflected). But our brain interprets black when there is an absence of light. Thus, blacklight is an oxymoron (unless by black light you mean something entirely different, which is ultraviolet light that interacts with objects and instead of reflecting it re-radiates the incoming light in a different frequency, such as the so called black light used in pubs and discos)
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$\begingroup$ Projecting darkness is clearly impossible, but if one uses "blacklight" to refer to "UV-A" the question would be interesting from that point of view as well. I would guess most lens materials would tend to absorb UV-A, but being able to project images with blacklight would be sorta neat. $\endgroup$– supercatCommented Mar 14, 2015 at 14:17
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$\begingroup$ Worth noting: the absence of light (i.e. shadow) has interesting properties that it could not have if it was actually light and could be emitted. For example, it is possible for a shadow to move faster than the speed of light (without violating any laws) $\endgroup$ Commented Oct 3, 2015 at 21:10